Total money nickles are worth of = $2.5
Let number of nickles coins be 'x'
Let number of dime coins be 'y'
Let number of quarter coins be 'z'
we have,
x + y + z = 100 and x = y +z
on solving the two equations, we get x = 50
1 nickle = 5 cents
50 nickles = 250 cents = $2.5
